Tests of Resolution

Binocular Tests

Before the appearance of stabilising binoculars it used to be thought that the best resolution available with the standard pair of 7 x 50 binoculars was around 25''. The limiting magnitude also improves with the field being more stable and again it would be most interesting to see what the limit of these instruments is. Table 2.1 lists a number of test objects.

Resolution Tests for Binoculars

Table 2.1 gives a list of 50 double stars that are suitable tests for image-stabilised (and other) binoculars. The pairs have been selected from the WDS with the criteria that the magnitudes should both be brighter than 8.0 and the separations lie between 8 and 25''. The pairs are well distributed around the sky so a number of them will be visible at any time of year. The positions are given for J2000 and the position angle and separation (in arcsec-onds and degrees respectively) refer to the date given in the previous column. In most cases the motion is very small but a number of these pairs are binary and are indicated by an asterisk (*) after the catalogue name. The magnitudes are visual and come from the WDS. The components AB refer to the brightest two stars in a multiple system. If no components are stated, this means that the given pair is a double only. For an explanation of the catalogue names, see Chapter 24.

Resolution Tests for Telescopes

Tables 2.2-2.7 present some tests of resolution for telescopes of apertures ranging from 90 mm to 60 cm.

Table 2.1.

Resolution tests for binoculars.

Catalogue

Component

RA(2000)Dec

Date

PA

Separation

STF3053

AB

00026+6606

1992

72

15.1

5.96

7.17

STF60*

AB

00491+5749

1999

318

12.7

3.52

7.36

STF100

AB

01137+0735

1994

63

23.2

5.22

6.15

H58

01590-2255

1991

303

8.5

7.28

7.56

STF205

A-BC

02039+4220

1995

64

9.8

2.31

5.02

STF239

02174+2845

1997

212

14.0

7.09

7.83

PZ2

02583-4018

1997

90

8.3

3.20

4.12

STF401

03313+2734

1998

270

11.5

6.58

6.93

STF550

AB

04320+5355

1996

309

10.5

5.78

6.82

STF590

04436-0848

1991

318

9.3

6.74

6.78

STF630

A-B

05020+0137

1997

50

14.4

6.5

7.71

STF688

05193-1045

1991

95

10.6

7.52

7.55

STF872

AB

06156+3609

1991

216

11.4

6.89

7.38

DUN30

AB-C

06298-5014

1994

313

12.0

5.97

7.98

HWE 13

06358-1606

1991

117

12.6

7.37

7.39

STF948

AC

06462+5927

1998

310

8.9

5.44

7.05

STF1044

07164+4738

1991

168

12.6

7.70

7.72

STF1065

07223+5009

1991

255

14.9

7.51

7.67

19

07343-2328

1991

117

9.8

5.82

5.85

STF1122

07459+6509

1991

186

14.9

7.78

7.80

STF1245

AB

08358+0637

1991

26

10.2

5.98

7.16

STF1315

09128+6141

1991

27

24.8

7.33

7.65

SHJ110

AC

10040-1806

1991

274

21.2

6.22

6.97

STT219

10302+5100

1991

300

14.1

7.56

7.70

DUN97

AB

10432-6110

1991

174

12.3

6.59

7.88

BSO6

11286-4240

1991

169

12.9

5.13

7.38

DUN117

AB

12048-6200

1994

150

22.7

7.40

7.83

STF1627

12182-0357

1993

196

19.8

6.55

6.90

STF1694

12492+8325

1997

329

21.5

5.29

5.74

STF1744

AB

13239+5456

1999

153

14.6

2.23

3.88

STF1821

14135+5147

1999

236

13.7

4.53

6.62

HJ4690

Aa-B

14373-4608

1991

25

19.3

5.55

7.65

STF1919

15127+1917

1995

11

23.4

6.71

7.38

LAL123

A-BC

15332-2429

1991

301

9.1

6.94

7.00

PZ4

15569-3358

1991

49

10.3

5.09

5.56

H7

AC

16054-1948

1991

20

13.6

2.59

4.52

DUN206

AC

16413-4846

1991

265

9.6

5.71

6.76

STF2202

AB

17446+0235

1994

93

21.0

6.13

6.47

STF2273

AB

17592+6409

1999

283

21.3

7.31

7.63

SHJ 264

AB-C

18187-1837

1991

51

17.3

6.86

7.63

STF2417

AB

18562+0412

1997

104

23.1

4.59

4.93

STF2474

Aa-B

19091+3436

1997

264

16.1

6.78

7.88

STF2578

AB

19457+3605

1995

125

15.0

6.37

7.04

SHJ324

20299-1835

2000

238

21.9

5.91

6.68

STF2727*

20467+1607

2000

266

9.2

4.36

5.03

Table 2.1.

Resolution tests for binoculars. (continued)

Catalogue

Component

RA(2000)Dec

Date

PA

Separation

STF2769

21105+2227

1999

299

18.0

6.65

7.42

STF2840

AB

21520+5548

2000

195

18.0

5.64

6.42

STF2873

AB

21582+8252

1996

69

13.6

7.00

7.47

DUN246

23072-5041

1995

255

8.8

6.29

7.05

These pairs are chosen because they appear to be moving fairly slowly at the present time and the following list should be accurate until about 2005. The pairs are chosen from the CHARA 4th catalogue of interfero-metric measures11 and the values given below are for the epoch 2002.0. The complete catalogue is available on the CD-ROM.

The closest pair in each list corresponds approximately to the Dawes limit for that aperture (11".6/D in cm) although the magnitude of both components varies so that the fainter and more unequal pairs will be more

Table 2.2.

Tests for 90-mm

aperture (HIP denotes the Hipparcos Catalogue number).

Catalogue

Component

RA(2000)Dec

HIP

PA

Separation

BU728

23522+4331

17655

8

1.20

8.04

8.32

STF367

03140+0044

5058

134

1.13

7.36

7.41

A 1606

13128+4030

64464

15

1.25

8.81

8.91

BU114

13343-0837

168

1.30

(8.05

8.1)

STF987

06541-0552

33154

177

1.30

6.39

6.55

STF2843

AB

21516+6545

107893

147

1.40

6.37

6.67

STF2583

19487+1148

97473

107

1.35

5.75

6.04

STF1291

08542+3034

43721

312

1.49

5.40

5.62

STF314

AB-C

02529+5304

13424

313

1.54

(6.5

6.7)

STF1932

15183+2649

74893

262

1.60

6.59

6.64

STF1639

AB

12244+2535

60525

324

1.67

6.41

7.55

Table 2.3.

Tests for 15-cm

aperture.

Catalogue

Component

RA(2000)Dec

HIP

PA

Separation

BU341

13038-2035

63738

311

0.75

5.58

5.62

BU316

04528-0517

22692

183

0.85

7.71

7.75

BU232

AB

00504+5038

3926

250

0.85

7.83

8.07

STF13

00163+7653

1296

53

0.90

6.35

6.60

STT403

20143+4206

99749

172

0.94

(7.3

7.5)

HO475

AB

22327+2625

309

1.05

(9.3

9.5)

BU694

AB

22030+4439

108845

3

1.10

5.57

7.66

Table 2.4.

Tests for 20-cm

aperture.

Catalogue

Component

RA(2000)Dec

HIP

PA

Separation

A 1504

AB

00287+3718

2252

41

0.54

8.12

8.22

HU517

AB

01037+5026

4971

29

0.56

8.22

8.27

A 347

14369+4813

11467

252

0.57

7.73

7.93

HO44

10121-0613

49961

204

0.58

7.96

8.27

COU482

14213+3050

1 22

0.60

(9.2

9.3)

HU149

1 5246+541 3

75425

273

0.60

6.68

6.80

BU303

01096+2348

5444

293

0.62

6.65

6.78

HU146

15210+2104

75117

1 27

0.66

8.82

9.09

BU991

22136+5234

1 40

0.66

(8.8

8.8)

STT435

2121 4+0254

105438

235

0.66

7.41

7.46

I 78

11336-4035

56931

98

0.67

5.39

5.44

A 185

22201+4625

319

0.69

(9.6

9.7)

STF412

AB

03345+2428

1 6664

356

0.70

5.95

5.98

STF2783

21141+5818

104812

355

0.70

7.11

7.34

STF1555

AB

11363+2747

56601

1 47

0.71

5.80

6.01

STF3056

AB

00046+3416

374

1 44

0.72

7.02

7.30

A 1116

15116+1008

74348

51

0.77

7.97

7.99

A 2419

03372+0121

96

0.78

(8.6

8.7)

KUI97

20295+5604

101084

132

0.79

5.89

8.77

BU182

AB

23171-1350

1 1 4962

47

0.79

8.16

8.38

A 1

01424-0646

7968

248

0.80

8.05

8.20

A 953

01547+5955

65

0.80

(8.8

8.8)

COU610

15329+3121

76127

200

0.82

4.14

6.55

STT112

05398+3758

49

0.84

(7.92

8.2)

difficult to resolve than the bright equal pairs of similar separation.

Note that these lists are merely suggestions for testing telescope objectives, and test objects should not be selected rigorously from one table. Resolution depends, after all, not only on the collimation and quality of the optics, but the state of the atmosphere. It is most likely that the last word on any attempts to resolve close pairs will be had by the seeing, so attempts should be made when atmospheric conditions are suitable.

References

1 Astronomical League http://www.astroleague.com/al/

2 Mullaney, J. and McCall, W., 1965 Nov., Sky & Telescope, The Finest Deep-Sky Objects, 280.

3 Mullaney, J. and McCall, W., 1965 Dec., Sky & Telescope, The Finest Deep-Sky Objects II, 356.

Table 2.5.

Tests for 30-cm

aperture.

Catalogue

Component

RA(2000)Dec

HIP

PA

Separation

VOU36

02513+0141

9

0.38

(8.4

8.9)

STT75

04186+6029

201 05

181

0.38

7.33

7.49

BU688

AB

21426+41 03

107137

1 97

0.38

7.55

7.61

A 1562

05373+4339

3

52

0.39

(9.0

9.0)

CHR91

20045+4814

98858

21 1

0.39

6.16

9.64

AC16

AB

1 9579+2715

98248

232

0.39

7.56

7.77

A 1588

09273-0913

46365

196

0.40

(7.2

7.3)

A 2152

AB

10290+3452

51320

50

0.40

8.52

8.79

RST4534

15089-0610

74116

12

0.41

(8.21

8.2)

RST4220

03038-0542

1 4255

339

0.42

8.85

8.91

A 2719

06203+0744

30120

65

0.44

6.76

6.83

MCA38

Aa

13100-0532

64238

339

0.44

4.38

6.72

STT349

17530+8354

87534

44

0.45

7.51

7.72

A 951

01512+6021

8629

220

0.45

7.98

8.26

A 914

00366+5608?

2886

26

0.46

7.97

8.05

BU1023

071 51+2553

35070

304

0.45

8.34

8.52

A 2016

AB

02287+0840

175

0.46

(9.9

9.9)

YSJ1

Aa

10329-4700

51504

95

0.46

5.02

7.39

BU1184

03483+2223

270

0.46

(8.9

9.1)

BU1298

16595+0942

83143

1 29

0.46

7.96

8.00

A 1607

13124+5252

64517

14

0.47

9.34

9.43

STT86

04366+1945

21465

4

0.47

7.32

7.34

I 450

01519-2309

222

0.48

(8.6

8.9)

STT337

1 7505+0715

87325

1 70

0.48

7.72

7.87

KUI8

02280+0158

1 1 474

38

0.52

6.45

6.66

HU1274

1 5550-1 923

77939

119

0.52

5.95

7.96

COU 103

15200+2338

283

0.54

(8.9

8.9)

STT510

AB

23516+4205

1 1 7646

304

0.55

7.34

7.41

Table 2.6.

Tests for 40-cm

aperture.

Catalogue

Component

RA(2000)Dec

HIP

PA

Separation

COU452

01 51 0+2551

8600

181

0.29

8.08

9.42

HU981

22306+6138

111112

21 5

0.29

6.98

7.23

COU1214

01373+4015

1 75

0.31

(9.6

9.6)

COU 1659

01298+4547

26

0.32

(9.0

9.3)

STF346

03055+2515

14376

254

0.34

5.45

5.47

BU1147

AB

23026+4245

113788

352

0.35

5.09

7.26

STT250

12244+4306

60522

349

0.35

7.88

8.02

HU520

01178+4946

1 66

0.36

(8.09

8.3)

A 1204

20143+3129

143

0.36

(9.4

9.7)

COU1510

02016+4107

131

0.36

(9.6

9.6)

COU2037

05219+3934

25060

1 43

0.37

7.31

7.54

KR12

01 41 5+6240

7895

291

0.37

7.81

7.88

A 1498

23594+5441

118287

90

0.38

7.73

7.77

Table 2.7.

Tests for 60-cm

aperture.

Catalogue

Component

RA(2000)Dec

HIP

PA

Separation

C0U2013

02520+1831

93

0.21

(9.1

9.1)

A 506

06357+2816

36

0.23

(8.6

8.9)

B 2550

AB

01425+5000

7979

277

0.23

8.41

8.58

COU 1505

00594+4057

4626

138

0.23

8.55

8.70

HO 98

19081+2705

93994

78

0.24

7.53

7.54

MCA60

Aa-B

20158+2749

99874

1 47

0.24

4.50

6.65

COU 1183

21180+3049

105146

18

0.25

8.13

8.30

4 Mullaney, J. and McCall, W., 1966 Jan., Sky & Telescope, The Finest Deep-Sky Objects III, 13.

5 Mitton, J. and MacRobert, A., 1989 Feb., Sky & Telescope, Colored Stars, 183

6 Adler, A., 2002 Jan., Sky & Telescope, The Season's Prettiest Double Stars, 131.

7 Adler, A., 2002 Jul., Sky & Telescope, More Pretty Doubles, 111.

8 Ropelewski, Michael, 1999, An Atlas of Double Stars, Webb Society; see http://webbsociety.freeserve. co.uk/notes/doublest01.html

9 Di Cicco, D., 1993, Mar., Sky & Telescope, The Delights of Observing Double Stars, 112.

10 Kaznica, J.J. et al., 1984, Webb Society Double Star Section Circular No 3.

11 Hartkopf, W.I., Mason, B.D., Wycoff, G.L. and McAlister, H.A., 2002; see http://ad.usno.navy.mil/wds/ int4.html

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